Burundi ( or ), officially the Republic of Burundi (Kirundi: Republika y'Uburundi, [buˈɾundi]; French: République du Burundi, [buʁundi] or [byʁyndi]), is a landlocked country in the African Great Lakes region of East Africa, bordered by Rwanda to the north, Tanzania to the east and south, and the Democratic Republic of the Congo to the west. It is also considered part of Central Africa. Burundi's capital is Bujumbura. The southwestern border is adjacent to Lake Tanganyika.

The Twa, Hutu and Tutsi peoples have lived in Burundi for at least 500 years. For more than 200 of those years, Burundi was an independent kingdom, until the beginning of the 20th century, when Germany colonised the region. After the First World War and Germany's defeat, it ceded the territory to Belgium. Both Germans and Belgians ruled Burundi and Rwanda as a European colony known as Ruanda-Urundi. Despite common misconceptions, Burundi and Rwanda had never been under common rule until the time of European colonisation.

Burundi gained independence in 1962 and initially had a monarchy, but a series of assassinations, coups and a general climate of regional instability culminated in the establishment of a republic and one-party state in 1966. Bouts of ethnic cleansing and ultimately two civil wars and genocides during the 1970s and again in the 1990s left the country undeveloped and its population as one of the world's poorest. 2015 witnessed large-scale political strife as President Pierre Nkurunziza opted to run for a third term in office, a coup attempt failed and the country's parliamentary and presidential elections were broadly criticised by members of the international community.

Burundi's political system is that of a presidential representative democratic republic based upon a multi-party state. The President of Burundi is the head of state and head of government. There are currently 21 registered parties in Burundi. On 13 March 1992, Tutsi coup leader Pierre Buyoya established a constitution, which provided for a multi-party political process and reflected multi-party competition. Six years later, on 6 June 1998, the constitution was changed, broadening National Assembly's seats and making provisions for two vice-presidents. Because of the Arusha Accord, Burundi enacted a transitional government in 2000. In October 2016, Burundi informed the UN of its intention to withdraw from the International Criminal Court.

Burundi remains an overwhelmingly rural society, with just 13% of the population living in urban areas in 2013. The population density of around 315 people per square kilometre (753 per sq mi) is the second highest in Sub-Saharan Africa. Roughly 85% of the population are of Hutu ethnic origin, 15% are Tutsi, and fewer than 1% are indigenous Twa. The official languages of Burundi are Kirundi, French and English, Kirundi being recognised officially as the sole national language.

One of the smallest countries in Africa, Burundi has an equatorial climate. Burundi is a part of the Albertine Rift, the western extension of the East African Rift. The country lies on a rolling plateau in the centre of Africa. The highest peak, Mount Heha at 2,685 m (8,810 ft), lies to the southeast of the capital, Bujumbura. The most distant source of the River Nile is the Ruvyironza River in the Bururi Province of Burundi, the Nile is linked from Lake Victoria to its headwaters via the Kagera River to the Ruvyironza River. Another major lake is Lake Tanganyika, located in much of Burundi's southwestern corner. There are two national parks, Kibira National Park to the northwest (a small region of rain forest, adjacent to Nyungwe Forest National Park in Rwanda), and Ruvubu National Park to the northeast (along the Rurubu River, also known as Ruvubu or Ruvuvu). Both were established in 1982 to conserve wildlife populations. Burundi's lands are mostly agricultural or pasture.

Settlement by rural populations has led to deforestation, soil erosion and habitat loss. Deforestation of the entire country is almost completely due to overpopulation, with a mere 600 km2 (230 sq mi) remaining and an ongoing loss of about 9% per annum. In addition to poverty, Burundians often have to deal with corruption, weak infrastructure, poor access to health and education services, and hunger. Burundi is densely populated and has had substantial emigration as young people seek opportunities elsewhere. The World Happiness Report 2018 ranked Burundi as the world's least happy nation with a rank of 156.